Slide 2 Overview In this chapter we will be focusing on our “input systems”, the senses we use to perceive the world around us. We will focus primarily on vision, but will also discuss audition, touch and smell. Much of the information will attempt to explain how these systems work … though we will also discuss illusions that show us how our sensory systems can be tricked. Throughout, we will again emphasize the distinction between sensation , the information arriving through the sense organs, and perception , the subjective impression of the world that we end up with. Chapter 6 - Sensation

Slide 3 Sensation versus Perception The textbook actually defines sensation and perception slightly differently from how I have, though the flavour is the same. According to the text: Sensation is the detection of simple stimulus properties such as brightness, colour, sound frequency, sweetness. Perception is the detection of objects, their location, their movements, their background. Thus, seeing purple and blue in the picture is sensation, whereas seeing beautiful fireworks is perception Chapter 6 - Sensation

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Slide 4 Transduction Transduction is the process by which sense organs convert energy from environmental events into neural activity … eventually ending up in the brain. Sense organs differ in terms of the kinds of environmental energies they are sensitive to, and in the manner they transduce that energy. Usually the transduction is accomplished via specialized receptor cells that release specialized neurotransmitters that stimulate other neurons. Steve, show table 6.1 here to show some of the variety across the sense organs Chapter 6 - Sensation

Slide 5 Sensory Coding As we discussed earlier, nerve cells can only send a message or not. The message does not vary in terms of what it says, or how it says it. So how then can the same nerve cells transmit the fact that bananas are yellow, but carrots are orange? The answer lies in the use of code … think of Morris Code for example. In Morris Code complex semantic messages were transmitted using simple clicks Chapter 6 - Sensation

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Slide 6 How does the Brain Code Information? The first answer to this question is: We’re not absolutely sure yet … the puzzle still needs more unraveling. But, we do think the following two codes are involved. Anatomical Coding- Sensory organs located in different parts of the body send their signals to different locations in the brain … the brain uses this to interpret the signals correctly. Temporal Coding- Information can be coded according to time. The easiest way to do this is with respect to rate of neural firing. May be the main way to code the intensity of stimulation Chapter 6 - Sensation

Slide 7 Psychophysics - Physics of the Mind The systematic study of the relation between the physical characteristics of stimuli, and the sensations they produce.

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